Armor piercing,sabot shells



April 21, 1970 w. GROLLY ARMOR rmncme SABOT SHELLS Filed June 28, .1967

United States Patent 3,507,221 ARMOR PIERCING, SABOT SHELLS Walter Grolly, Geneva-Vernier, Switzerland, assignor to Brevets Aero-Mecaniques S.A., Geneva, Switzerland Filed June 28, 1967, Ser. No. 649,722 Claims priority, application Luxemburg, July 21, 1966,

Int. Cl. F421; 11/14, 13/04 US. Cl. 102-52 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to armor piercing shells for a gun having its barrel provided with riflings, such .a shell including a core of a metallic material of high density and great hardness (such in particular as tungsten carbide) housed in a detachable sabot made of a light material, that is to say, a material of a density substantially lower than that of steel, in particular an aluminum alloy and possibly a plastic material, this sabot comprising a cylindrical envelope surrounding the core which is maintained at the rear by the bottom of said sabot and held at the front by locking means retractable when the shell is launched.

It is known that such a sabot is adapted to travel together with the core at the beginning of the trajectory and, subsequently, to separate therefrom. Projectiles of this kind permit of launching with a high initial velocity cores of a calibre smaller than that of the gun, their sabots acting both as packing means for the powder gases in the barrel of the gun and as means for transmitting the spinning movement to the core.

The chief object of the present invention is to provide a projectile of this kind wherein the conditions of separation of the sabot from the core are more uniform, which involves a higher accuracy in shooting.

For this purpose, the shell according to this invention is characterized in that the locking means cooperate with a transverse bearing surface provided at the front part of the core cylindrical body, this surface being preferably obtained by a reduction of the diameter of the core ahead of said transverse surface.

According to a preferred embodiment, the inner diameter of the sabot and the outer diameter of the cylindrical portion of the core are substantialy equal and the bottom of the sabot is provided with a hole of a diameter sufficiently great to prevent any substantial dash-pot effect which would interfere with the relative frontward movement of the core with respect to the sabot, but sufficiently small in order that, on the one hand, the pressure of the gases in the gun barrel, acting upon the portion of the core located opposite said hole, does not tend to drive out the core from the sabot and, on the other hand, the sabot bottom can transmit its spinning movement to the core.

A preferred embodiment of the present invention wi l be hereinafter described with reference to the appended drawings given merely by way of example and in which,

FIG. 1 shows, half in elevation and half in axial section, an armor piercing shell according to the present invention;

3,507,221 Patented Apr. 21, 1970 FIG. 2 shows, on an enlarged scale, a detail of FIG. 1, the sabot being locked with respect to the core;

FIG. 3 is a view similar to FIG. 2 but wherein the locking means between the core and the sabot have been brought into inoperative position; and

FIG. 4 is a plan view of the ring through which the core and the sabot are locked together.

The shell comprises a core 1 of a high density metallic material, such as tungsten carbide, housed in a sabot 2 of a light material such as an aluminum alloy. This sabot 2 comprises a cylindrical tubular portion 2a and a bottom 2b. Core 1 is held inside sabot 2 by the bottom 2b thereof, which prevents relative motion of said. core toward the rear and by a locking device which prevents relative motion of the core toward the front and is adapted to be retracted when the shell is launched. Cylindrical tubular portion 2a is provided with a rotating band 3 intended to cooperate with the helical riflings of the gun barrel and with an annular groove 4 for setting thereof into a cartridge case. Core 1 comprises a cylindrical portion 1a- 1c and an ogive 111.

Now, according to the present invention, the locking device cooperates with a transverse bearing surface 5 provided near the front end of themain cylindrical portion In of core 1 and which consists of a shoulder extending between said main portion 1a the diameter of which is D FIG. 1) and a small length portion portion 10 of a diameter d smaller than D, the ogive 1b being located at the front end of said cylindrical portion 1c.

In the embodiment shown by the drawings the locking device consists of a split ring 6, provided with a slit 6a (FIG. 4), the inner edge of which rests upon cylindrical portion 1c and the rear surface of which bears upon transverse surface 5. This ring 6 is housed in a groove 7 limited at the rear by a shoulder 8 of sabot 2 and at the front by the rear edge of a sleeve 9 secured to said sabot 2. This sleeve 9 isprovided with external screw threads cooperating with screw threads carried by the front portion of sabot 2. The inner diameter of sleeve 9 is equal to that of sabot 2 and the outer diameter of said sleeve 9 is equal to that of sabot 2. The sabot 2 together with the sleeve 9 form a unit which is referred to in the specification as a case. The height of groove 7 in the axial direction is slightly greater than the thickness of ring 6 and its depth in the radial direction is at least equal to the maximum width of ring 6, whereby when said ring 6 expands under the effect of the centrifugal force due to the spinning of the shell, it expands outwardly into groove 7 (FIG. 2) and releases core 1.

A cap 10 of a light material intended to improve the aerodynamic outline of the core is fitted to the front thereof. This cap 10 is provided with a rear extension 11 fitting in the annular space left between the cylinddrical portion 10 of the core and the inner surface of sleeve 9.

The inner diameter of sabot 2 and the outer diameter D of the main tubular portion 1a of the core are given substantially equal values, whereby sabot 2 can slide rearwardly with respect to core 1 while being guided thereon.

Furthermore, the bottom of sabot 2 is provided with a hole 12 of a diameter a sufiiciently great to prevent any substantial dash-pot effect which would interfere with a relative frontward movement of core 1 with respect to sabot 2. However, this hole 12 is relatively small so that, on the one hand, the pressure of the gases in the gun barrel, tending to push the rear end of core 1 located opposite said hole 12, cannot drive out core 1 from sabot 2 and, on the other hand, the remaining portion of sabot bottom 2b can transmit to the core the spinning movement imparted to sabot 2 by the rifiings of the gun barrel penetrating into rotating band 3.

If the "bottom 2b of sabot 2 were not provided with hole 12, core 1, being given its length where it is in tight contact with sabot 2, would act as a pump piston in the cylinder formed by said sabot 2. In other words, in the absence of hole 12, the relative movement of core 1 in sabot 2 would create, at the rear of said core, a suction which might interfere with, or even prevent separation between said elements 1 and 2. It is what has been calledhereinabove the dash-pot effect.

In order to determine the value of the diameter a of hole 12,-itis necessary to determine, on the one hand, as a function of the mass of core 1 and of the maximum acceleration in the gun barrel, the inertia forces tending to. apply core 1 against the bottomZb of sabot 2, and, on the other hand, as a function of the maximum pressure of the powder gases in the gun barrel and of diameter a, the forces which tend to drive out core 1 from sabot 2. The first forces must of course be greater than the second ones. Another condition concerning the drive in rotationof core 1 can easily be determined as a function of the friction coefiicient of the material of core 1 with respect to that of the bottom 2b of-sabot 2.

When the shell is to contain a tracer composition 13, the latter is advantageously packed in a recess 14 provided at the rear of core 1 and opening opposite hole 12.

This shell works as follows: When handling it and in particular when it. is being introduced into the gun breech, core 1 is well maintained in sabot 2, in particular at the front by ring 6 (FIG. 2). When the shot is fired, sabot 2 is set spinning and drives, together with it, core 1 and ring 6. Under the effect of the centrifugal force the latter is then wholly expanded into groove 7 (FIG. 3). Due to the head resistance resulting from travel through the atmosphere, sabot 2 is retarded more than core 1 and quickly separated therefrom, being guided axially during this separation so that the trajectory of the core is not disturbed. Owing to the presence of hole 12, on the one hand, the separation between the two elements is not opposed by a dash-pot effect and, on the other hand, tracer composition 13 is ignited by the hot gases in the gun barrel without requiring a special igniting device.

An annular empty space might be provided inside sabot 2, the inner wall of which would thus be in contact with the cylindrical surface of the portion 1a of the core only over two separate areas of its length.

Furthermore, sabot 2 might be fitted on the outside and at the front thereof, with a thin steel ring adapted to prevent too deep a depression of the rifiings of the gun barrel into the light metal of sabot 2.

Finally, hole 12 might be stopped initially by a thin protection sheet adapted to be destroyed, when the shot is fired, by ignition from the powder gases.

What I claim is: l. A spinning armor piercing shell comprising: a core of a very hard and high density metallic material including a rear cylindrical portion and a front cylindrical portion, coaxial with, of smaller diameter than, and disposed in front of, said rear cylindrical portion, with a transverse bearing surface delimiting said rear and front cylindrical portions from each other, the diameter of said core atany given point being at least as great as the diameter of said core at any other point situated in front of said given point,

a case detachably surrounding said core and comprising a sabot and a sleeve secured at the front of said sabot,

said sabot being made of a light material and comprising a cylindrical tubular portion surrounding said rear cylindrical portionof the core and a bottom applied against the rear end of said core, the inner diameter of said sabot and the diameter of the core rear cylindrical portion being substantially equal so that said core fits in said sabot, and the bottom of said sabot being provided with a hole,

said case having, on its inner surface, an annular groove defined by afront transverse bearing surface of said case and a rear transverse bearing surface of said case, said front transverse bearing surface of said case being formed by a rear surface of said sleeve, and said rear transverse bearing surface of said case being formed by a surface of said sabot and lying in the same transverse plane as, and forming a continuation of, the transverse bearing surface of said core,

and locking means in the form of a ring substantially surrounding said front cylindrical portion of said core, the rear of said ring being applied, at rest, against said transverse bearing surface of said core, andsaid ring extending, at rest, into said annular groove for co-operating therewith, whereby said ring, when at rest, prevents forward movement of said core with respect to said case,

said ring being expansible by the centrifugal force acting thereon when the shell is set spinning, and said groove being adapted to receive said ring in its entirety when said ring is expanded by said centrifugal force, whereby to release said case from said core.

2. A shell according to claim 1, wherein said ring is a split ring.

3. -A shell according to claim 2 wherein said sleeve is secured in the front part of said sabot and includes, at its front, a flange the outer diameter of which is equal to the outer diameter of said sabot, the inner diameter of said sleeve being substantially equal to the inner diameter of said sabot.

4. A shell according to claim 3 further comprising an ogive-shaped cap including a rear tubular extension fitting in and substantially filling, except for the region of said locking ring, the annular space between said core front cylindrical portion and the inner wall of said sleeve.

5. A shell according to claim 1 wherein said core is provided, in the rear part thereof, with a recess opening into the rear face of said core through said hole, further comprising a tracer composition in said recess.

References Cited UNITED STATES PATENTS 581,946 4/1897 Semple 102- 7 1,294,604 2/1919 BerentSen 1()29 3 2,998,778 9/1961 Hablutzel 102-593 3,000,316 9/1961 Dunlap et al. 102-93 3,359,905 12/1967 Engel 102-93 3,186,342 6/1965 Hancock 102 93 BENJAMIN A. BORCHELT, Primary Examiner J. FOX, Assistant Examiner U-S- L X-R, 

